In the assembly of wallboard panels to form a wall, the trend is to provide predecorated panels which, when abutted edge to edge, form a joint which is not given a conventional coating of joint compound, but is left exposed. Such predecorated panels may comprise, for example, a gypsum core enveloped by a vinyl film, which displays a solid color or a patterned decoration. One example of such a panel is disclosed in U.S. Pat. No. 3,265,547.
As the joints between such panels are not further treated, the edge configuration of the panels is critical. Any deviation of the edge from an essentially planar surface results, when the edge is abutted against another panel of like design, in a gap between the panels. Such gaps are not only aesthetically unacceptable, they also contribute to loss of sound and thermal insulation.
Conventional predecorated gypsum panels have been prone to such gapping when assembled, for a number of reasons. Not only is it impossible to control manufacturing tolerances to produce only true, perfectly planar edge surfaces, deviations occur also because of damage to the edge surfaces during shipping. Also, gapping will occur if the panels are not erected with perfect vertical alignment. Thus, a gap or open area having edge separations as large as one thirty-second or one eighth of an inch may result from the assembly of conventional predecorated gypsum wallboard.
The conventional approach in overcoming such gapping is to rely on field expedients. For obvious reasons, the gapping does not become apparent until assembly of the panels, and the contractor may seek to correct it by jamming or hammering panels into closer contact, thus further damaging the edges of the panels. Such on-site solutions are therefore unacceptable.
Still another problem with conventional predecorated wallboard has been that the rigidity and non-adjustable width of the paneling has made it impossible to line up the wall joints with ceiling joints such as occur in suspended ceilings.
One approach that has been taken to avoid the problem is to wrap the decorative sheet around the edges so as to leave an air gap between the sheet and the core edges along the entire length of the edges. An example of such a construction is shown in U.S. Pat. No. 3,226,284. The difficulty with such an approach is that the sheet, by being unsupported at the edges, collapses upon assembly of the panels edge to edge to the point at which beading results. "Beading" is the protrusion of the sheet out of the general plane of the rest of the sheet, creating an unsightly ridge. It is thus necessary that a solution be found which will not create the unacceptable alternative of "beading."
A resilient edging has been provided in insulation panels used in refrigerated vehicles, of which U.S. Pat. No. 3,141,206 is an example. Such a construction, however, has not been used in a predecorated gypsum wall panel.